The Mediant Triad

There isn't much to say here, but we'll cover it anyway.

• The mediant triad is build on Scale Degree 3
• It is major in the minor mode and minor in the major mode (like the submediant triad)
• The chord's generic function is... complicated.

Building a Mediant Triad

This triad is simple enough to build

In the Major mode

• Scale degrees 3. 5, and 7 (Mi, Sol, Ti)
• The quality is minor

In the Minor mode

• Scale degrees 3, 5, and 7 (Me, Sol, Te)
• The quality is Major

Like the submediant triad, this chord is ALSO built on different absolute pitches for the two modes, major and minor. and again, Luckily, this changes nothing about how the chord functions.

What Note Do You Double?

This chord follows the same doubling rules as any other chord: you must **double for function. **

So what is the function?

The mediant triad is special because it is so weak.

In the common practice period (approx. 1700-1800), this triad is not that common.

Like the submediant triad, it is a bit more of an embellishing harmony. Both triads share pitches with some very strong fundamental harmonies. However, the submediant triad found its place. The mediant triad never really did.

Note: in modern popular music, the mediant triad is currently seeing its golden era. It can be a beautiful chord, but it just isn't that common in the CPP.

The Mediant as a Predominant Harmony

This chord may be used as the weakest predominant harmony.

So now the order from weakest to strongest:

iii -> vi -> IV -> ii

However, you will very rarely see this chord go directly to V (at least in root position). If this chord does show up as a predominant harmony, it will typically precede the submediant or subdominant harmony.

So that is the natural place for the mediant triad. It most commonly precedes IV or vi (or iv or VI). This is the most common way you will see this chord in both the CPP and in today's popular music.

The Mediant as a Tonic Harmony

This chord may be used as the weakest tonic harmony.

So, it seems like the mediant triad is a suitable early predominant harmony, but not a suitable late predominant harmony. For me, the predominant portion of a chord progression can begin with iii, but not end with it.

My rationale for this is that the chord also acts as a weak tonic substitute. This is because it shares two notes with the tonic triad. You will essentially never see this used as a tonic substitute in the classical style, though in jazz music this chord will occasionally substitute for tonic.

However, we will never see it in this way in this class.

The Mediant as a Dominant Harmony

This chord, when seen in first inversion, is best understood as exhibiting dominant function. This is true in all types of music.

This is best understood as an embellishment of the V chord.

How can it be all three??

This chord unfortunately has two issues.

It shares two notes with the all-star tonic harmony. Mi and Sol when heard together are MUCH MUCH more likely to be interpreted as part of the tonic triad. (Remember, we will always hear the simplest version of something). This is why it really cannot act as a good predominant harmony, as it has the chains of tonic function restricting it.

It also shares two notes with the all powerful dominant harmony. Sol and Ti when heard together are MUCH MUCH more likely to be interpreted as part of the dominant triad. In fact, when this chord is in first inversion, it is better understood as a V chord with a non-harmonic tone Mi.

Because the function of the mediant triad is being pulled in so many directions, it's function is weakened significantly. The function of this chord is so weak that the function of the notes themselves (Sol is a very strong note when it is in the bass) overtake it. We will revisit this idea of a function being overtaken, when we talk about sequences. You will see that the mediant triad shines during harmonic sequences.

This is also why it mostly only appears as an early predominant function and in root position. This is the perfect situation for this chord:

• It is in root position, the strongest version of the chord
• It precedes a chord either by step (subdominant) or by fourth (submediant). Motion by fourth is the strongest motion between chords, then motion by step, then motion by third.

So the mediant triad really doesn't have a home in the classical era, it is mostly an embellishing harmony. When done well though, it can be beautiful!